In prior art, the cultivation of leaf vegetables in greenhouses is based on the use of, for example, elongated pipes, the side surface of the pipe being equipped with openings, in which seedlings are placed. The seedlings of plants are placed in the openings in the pipe, each seedling with a root ball consisting of e.g. soil. Normally, the root ball is also enclosed in a supporting structure, which is e.g. a mesh-like pot. Said pot is made of, for example, plastic, but also compressed peat or the like can be applied. The seed of the plant is sowed in said pot which has first been filled with e.g. peat. The peat is used as the growing substrate for the seed and the seedling. The pots are placed in cells which are brought for germination into e.g. a chamber at a suitable temperature and under conditions favourable for germination. The cells are, for example, boxes equipped with cavities for the pots. After the germination, the cells are placed on a seedling table, where the seedlings are irrigated from above. After this, the pots with the germinated seedlings are removed from the cells and placed in openings in the pipes.
A seedling that has grown to a sufficient size, with its root ball and the pot, is placed in the pipe, whose openings have room for several seedlings in succession. The pipe is placed on a cultivation table in a greenhouse, where the seedling of the plant is allowed to grow until the plant is ready for harvesting. Normally, automatic cultivation tables are used, which automatically take care of the irrigation of the plants and transfer the pipe forward, wherein the direction of movement is transverse to the longitudinal direction of the pipe. Furthermore, the seedling tables change the distance between the pipes so that when the plant grows in size, the distance between the pipes is also increased automatically. Normally, at the initial end of the cultivation table, the seedlings are placed in the pipes, and the pipes are also as close to each other as possible; and at the terminal end of the cultivation table, the plants are collected from the openings of the pipes, together with the root ball and the pot, and the pipes are spaced from each other. The empty pipes are brought to the initial end of the table for filling again, possibly preceded by washing of the pipes.
The pipe used for growing is, for example, a tubular structure whose top surface has been drilled or punched to provide openings, in which the seedlings, together with the root ball and normally also with a pot, can be inserted firmly. The roots of the seedling, which are in the root ball, are placed inside the pipe, to which irrigation water is led. The roots of the seedlings take in the water they need, and excess water can be drained along the pipe. In an example, irrigation water with nutrients is led into the pipe via its first end, and excess irrigation water is drained from the pipe via its opposite second end. The pipe is made of, for example, plastic, by applying, for example, extrusion as the manufacturing method.
Publication DE 8901847 U1 presents an example of a pipe used for cultivation, where the bottom part and the top of the pipe are made of two different pieces which are joined together. The cover is provided with punched holes, in which the seedling and its root ball as well as the pot enclosing the root ball can be inserted.
The cross-section of the bottom part of the pipe can be, for example, a U shape or an H shape, with either vertical or slightly slanted side walls. The shape of the bottom of the bottom part is, for example, horizontal or a V shape.
The use of the pot, the filling of the pot with peat, the sowing of a seed in the peat, moving the pot to the germination process and from it to e.g. a seedling table (utilizing e.g. cells which hold several pots in the process), and further moving the seedling with its pot into the openings of the pipe and onto the cultivation table, and finally, for the harvesting, also removing the finished plant with its pot from the pipe, are steps of cultivation of plants, for example, in greenhouses, in the case of cultivation of leaf vegetables and particularly lettuce. It is difficult to automate the above presented steps, or to reduce them in number, for efficient cultivation.